The present invention relates to permutation locks in general, and more particularly to improvements in permutation locks of the type wherein the tumblers may constitute or resemble discs and are movable to predetermined positions by a rotary actuating unit which includes a cam having a peripheral notch or cutout for a portion of a locating device which is articulately connected with the locking bolt and can be moved into engagement with the tumblers only when the tumblers assume predetermined angular positions corresponding to the selected combination.
Permutation locks of the above outlined character are described in German Offenlegungsschriften Nos. 23 20 816 and 28 16 969. The locks which are disclosed in these publications are constructed and assembled in such a way that the locking bolt can be moved to its extended position in response to rotation of the cam while the tumblers remain in the aforementioned predetermined angular positions. This contributes to convenience of manipulation of the permutation lock because it is not necessary to adjust the positions of the tumblers prior to each opening of the lock, i.e., prior to each retraction of the locking bolt from its extended position. However, such mode of operation also reduces the reliability of the permutation lock, i.e., an unauthorized person is much more likely to rapidly open the lock than if the positions of the tumblers necessitate adjustment prior to each retraction of the bolt.